This invention relates to adjustable wrenches; and more particularly relates to a novel and improved adjusting mechanism for open-end wrenches of the crescent type.
Crescent wrenches employ a movable jaw at one end which can be loosened or tightened by rotation of a worm gear associated with the movable jaw by grasping between a finger and thumb. It has been proposed in the past to employ a slide mechanism in the handle of the wrench which operates through a helical shaft to cause rotation of the worm and, for example, reference is made to U.S. Pat. No. 3,555,939 to K. F. Halls. In Halls, the helical shaft; in the handle has a bevel gear at one end which intermeshes with a bevel gear at the end of the worm, and the slide mechanism includes a thumb button control which is assembled in an elongated slot along one side of the handle to engage the helical shaft and impart rotation by advancing along the slot.
Wrenches of this type which have been designed in the past have suffered certain drawbacks owing to a tendency of the thumb button to jam and, at least in certain sizes of wrenches, is not capable of imparting sufficient rotational force through the helical shaft to adequately tighten the movable jaw. Moreover, wrenches with a single thumb button control are typically designed for right-hand use only and cannot be effectively used by a left-handed person.
Accordingly, it is proposed to overcome problems associated with adjustable jaw wrenches of the type described by devising a slide mechanism which can be operated or manipulated from either or both sides of the handle and in such a way as to minimize the possibility of jamming or inadequate tightening but nevertheless enable use in close quarters. Most importantly, however, greater leverage can be effected while enabling use of the wrench by either hand.
Other representative patents in this field are U.S. Pat. Nos. 3,368,432 to K. F. Halls, 3,541,899 to J. H. Tanner, 3,640,159 to K. F. Halls et al, 3,673,896 to H. W. Vardaman, 3,901,107 to K. F. Halls, 4,046,034 to H. J. Fiewelling, 4,766,786 to M. Jeremic, 4,907,476 to R. P. Singleton and 4,913,007 to R. W. Reynolds.